Question

Suppose there is a steady current in an inductor. If you attempt to reduce the current to zero instantaneously by quickly opening a switch, an electrical arc can appear at the switch contacts. Why? Indeed, is it physically possible to stop the current instantaneously? Explain.

Answer 1

Inductors can be thought as magnetic capacitors. If you break the circuit by opening a switch, the energy stored in the magnetic field will try to oppose the change in current so, the 'magnetic capacitor' will start to discharge itself. Remember that current doesn't flow through an open circuit (such as the one with an open switch), so an electric arc will appear at the contacts of the switch to temporarily close the circuit and release the energy stored inside the inductor.